KR20200009074A - Method for measuring magnetic strain rate of steel sheet in annealing furnace, magnetic strain rate measuring device, continuous annealing process, continuous hot dip galvanizing process - Google Patents

Abstract

Provided are a magnetic strain rate measuring device and a method for measuring magnetic strain rate of a steel sheet in an annealing furnace, and also a continuous annealing process and a continuous hot dip galvanizing process to which the magnetic strain rate measuring method and magnetic strain rate measuring device are applied. The steel sheet is heat-treated in the annealing furnace by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. As a method of measuring the magnetic transformation rate of a steel sheet beforehand, an AC drive signal is transmitted to the surface of the steel plate by a drive coil having a size greater than or equal to the plate width using the air core, and the drive signal reflected from the steel plate is used for the air core. Measured by a receiving coil having a size greater than or equal to the width of the plate, the measurement processing device corrects the distance between the steel plate and the drive coil by using the measured value of the drive signal measured by the receiving coil, and based on the corrected distance, Measure the metamorphosis rate.

Description

Method for measuring magnetic strain rate of steel sheet in annealing furnace, magnetic strain rate measuring device, continuous annealing process, continuous hot dip galvanizing process

This invention belongs to the measurement of the magnetic transformation rate of the steel plate in a continuous annealing furnace, and especially relates to the magnetic transformation rate measuring method of a steel plate, and a magnetic transformation rate measuring apparatus. The present invention also relates to a continuous annealing process and a continuous hot dip galvanizing process to which the magnetic strain rate measuring method and the magnetic strain rate measuring apparatus of the present invention are applied.

In recent years, from the viewpoint of the weight reduction of automotive steel sheets, there is a high demand for providing steel sheets having high strength and excellent workability. In order to obtain the high strength and high workability of a steel plate, cooling is performed in the state which made the steel plate into the ratio of the specific (gamma) phase (austenite phase) and (alpha) phase (ferrite phase). Therefore, grasping the ratio of each phase of a cooling start point is advantageous in order to achieve the characteristic of a steel plate suitably.

Conventionally, as a method for grasping the ratio of each phase, a magnetic detector, that is, an apparatus for measuring the magnetic transformation rate of a steel sheet has been used (see Patent Documents 1 and 2). Patent Literature 1 discloses an apparatus comprising a drive coil for generating a magnetic field and a detection coil for measuring a magnetic field transmitted through a steel sheet as an apparatus for measuring a magnetic transformation rate. Patent Literature 2 discloses an apparatus comprising a drive coil for generating a magnetic field and a detection coil for measuring a magnetic field reflected from a steel sheet as an apparatus for measuring a magnetic transformation rate.

Japanese Laid-Open Patent Publication No. 56-82443 (1st, 2nd page, Fig. 1) Japanese Laid-Open Patent Publication No. 59-188508 (figure 2)

Measuring the ratio of the austenite phase and the ferrite phase of steel, that is, the transformation rate, is advantageous in hot rolling as well as important in the annealing process of high strength cold rolled steel sheet, as described in the prior art. Also in the annealing process of a high strength cold rolled sheet steel, the measuring method similar to the case of hot rolling can be applied as a measuring method of a transformation rate.

However, in the measuring method using the measuring device described in Patent Document 1, as described on page 6 of Patent Document 2, the distance between the steel sheet and the measuring device is determined from the viewpoint of optimizing the penetration depth of the magnetic flux into the magnetic body. There was a problem that it must be made small. Therefore, when applying the measuring apparatus of patent document 1 to the annealing process of a high strength cold-rolled steel sheet, it must approach the steel plate in the annealing furnace which anneals at about 900 degreeC, and must provide a measuring apparatus, and it cools down a measuring apparatus. In consideration of this, it was impossible to reduce the distance between the steel sheet and the measuring device.

On the other hand, in the measuring method using the measuring apparatus (detection apparatus) described in patent document 2, since an excitation coil (driving coil) and a detection coil are arrange | positioned with respect to steel materials, the problem regarding said installation is overcome. However, in the case where the steel sheet is conveyed several times in the vertical direction as in the vertical annealing furnace, it is necessary to provide the measuring device halfway with respect to the height direction of the furnace. In this case, in order to support the measuring apparatus with a heavy iron core in a high temperature annealing furnace, the member with a large cross-sectional area is needed. Therefore, there existed a problem that the member with large cross-sectional area for supporting a measuring apparatus hinders heating and cooling of an annealing furnace.

In addition, since any of the measuring devices described in Patent Documents 1 and 2 is compact, in order to measure only the transformation rate of a part of the steel sheet and to measure the transformation rate over the entire sheet width of the steel sheet, a large number of measuring devices are moved in the plate width direction. There was also a problem that needed to be installed.

In recent years, in the manufacture of high strength steel sheets, the austenitic fraction is high. However, since the heating efficiency of the solenoid induction heating apparatus used for reheating in a continuous annealing furnace or reheating for the alloying of zinc in a continuous hot dip galvanizing line is low, the output of the induction heating apparatus is in a high state. Fluctuation of the austenite phase fraction of the steel sheet which does not occur occurs. As a result, temperature control became unstable. In particular, when the austenite phase fraction changes in the steel sheet, the solenoid type induction heating device generates electromotive force accompanying the magnetic change of the steel sheet, which causes sudden voltage fluctuations in the circuit and makes it impossible to control. There was. Since voltage fluctuations are caused by intrusion of the austenite phase fraction into the solenoid type induction heating device, it cannot be predicted in advance, and it is difficult to suppress the generated voltage fluctuations under control.

This invention is made | formed in view of such a situation, The continuous annealing process which applied the magnetic strain rate measuring apparatus and the magnetic strain rate measuring method of the steel plate in a continuous annealing furnace, and this magnetic strain rate measuring method and magnetic strain rate measuring apparatus, It is an object to provide a continuous hot dip galvanizing process.

MEANS TO SOLVE THE PROBLEM The present inventors recognized the following points as a result of earnestly researching in order to solve the said subject.

According to the present invention, a drive coil and a receiving coil, which are air-core and have a path crossing the plate width, are disposed on the same plane side with respect to the steel sheet in the annealing furnace, respectively, to generate an AC drive signal from the drive coil, It is a magnetic transformation measurement method of the steel plate which measured the transformation rate of the steel plate by measuring the reflected wave from a steel plate with a receiving coil.

In the present invention, in the case of using the reflected wave, two receiving coils are paired, and the two receiving coils are arranged in symmetrical positions with the driving coils interposed therebetween, and connected in reverse phase, thereby preventing the magnetic change of the steel sheet. It is easy to discriminate the signal change caused by the signal. In the case of using two sets of the above-mentioned pairs of receiving coils, the two sets of receiving coils are different from each other by using the steel plates and the driving signals received and measured by the two sets of receiving coils by varying the distance between the receiving coils and the driving coils. The magnetic permeability signal is corrected by calculating the distance of the receiving coil.

In addition, the present invention extracts a component having a phase of 90 ° with respect to the transmitted drive signal from the drive signal measured by the receiving coil, and calculates the transformation rate using the magnitude of the component having the phase of 90 °. . Moreover, this invention divides the drive signal measured by the receiving coil into 0 degree phase component and 90 degree phase component on the basis of the transmitted drive signal, and calculates a transformation rate by using the ratio of the phase component.

Moreover, this invention arrange | positions the drive coil and receiving coil which comprised the closed circuit of the large area as crossing the plate width direction of a steel plate in an annealing furnace, respectively, and does not use a core material for each coil, Magnetic transformation measurement device.

Moreover, this invention is a continuous annealing process and a hot dip galvanizing process which perform the magnetic transformation measurement of this invention before induction heating, and perform feedforward control which considered the influence by the magnetization of a steel plate.

This invention is completed based on the above recognition, The summary is as follows.

[1] annealing steel sheet by using a drive coil disposed on one side of the surface of the steel sheet, and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. A method of measuring the magnetic transformation rate of a steel sheet before heat treatment at

By the drive coil which has the magnitude | size larger than the plate width using a hollow core, an AC drive signal is sent to the surface of a steel plate,

The drive signal reflected from the steel sheet is measured by a receiving coil having a size equal to or greater than the width of the plate using an air core,

An annealing for correcting the distance between the steel plate and the drive coil using a measurement value of the drive signal measured by the receiving coil by a measurement processing device and measuring the magnetic transformation rate of the steel plate based on the corrected distance Method for measuring the magnetic transformation rate of the steel sheet in the furnace.

[2] The receiving coil is a steel sheet in the annealing furnace according to [1], in which two receiving coils are paired and connected in a reverse phase to a position symmetrical with respect to the driving coil to measure the reflected drive signal. Method of measuring magnetic transformation rate.

[3] As the receiving coil, two sets of two receiving coils connected in reverse phase are used, and the distances of the two sets of receiving coils and the driving coils are differently arranged, respectively.

By the said measurement processing apparatus, based on the measured value of the said drive signal in the said two sets of receiving coils, each distance of the said steel plate and said receiving coil is computed, and the said magnetic transformation rate is based on the calculated result. The magnetic transformation rate measuring method of the steel plate in the annealing furnace as described in [1] or [2] which is correct | amended.

[4] annealing the steel sheet by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. A method of measuring the magnetic transformation rate of a steel sheet before heat treatment at

By the drive coil which has the magnitude | size larger than the plate width using a hollow core, an AC drive signal is sent to the surface of a steel plate,

The drive signal reflected from the steel sheet is measured by a receiving coil having a size equal to or greater than the width of the plate using an air core,

By the measurement processing device, the measured value of the drive signal measured at the receiving coil is divided into components having a phase of 90 ° with respect to the transmitted drive signal, and is based on the component having the phase of 90 °. A method of measuring the magnetic strain rate of a steel sheet in an annealing furnace for measuring the magnetic strain rate of a steel sheet.

[5] The measured value is divided by a component having a phase of 0 ° and a component having a phase of 90 ° with respect to the drive signal sent by the measurement processing device, respectively, and having a component having the phase of 0 °. The magnetic transformation rate measuring method of the steel plate in the annealing furnace as described in [4] which measures the said magnetic transformation rate based on the ratio of the component which has the said 90 degree phase with respect to.

[6] The steel sheet is annealed by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. A magnetic strain rate measuring device for measuring the magnetic strain rate of a steel sheet before heat treatment at

A drive coil for constructing a closed circuit having a large area having a size equal to or more than a plate width using an air core and transmitting an AC drive signal to the surface of the steel sheet;

A receiving coil constituting a closed circuit having a large area having a size equal to or greater than a plate width using an air core, and receiving and measuring the driving signal reflected from the steel sheet;

An annealing furnace having a measurement processing apparatus for correcting a distance between the steel plate and the driving coil by using the measured value of the drive signal measured by the receiving coil and measuring a magnetic transformation rate of the steel sheet based on the corrected distance Magnetic transformation rate measuring apparatus of the steel plate in the middle.

[7] The magnetic transformation rate measuring apparatus of the steel sheet in the annealing furnace according to [6], wherein the receiving coils are connected in reverse phase to two receiving coils in pairs and symmetrical with respect to the drive coils.

[8] The method according to [6] or [7], in which two sets of two receiving coils connected in reverse phase are used as the receiving coils, and the distances of the two sets of receiving coils and the driving coils are different from each other. An apparatus for measuring magnetic strain rate of a steel sheet in an annealing furnace.

[9] The reception coil according to any one of [6] to [8], wherein the number of windings of the coil is changed for each of the receiving coils, and the distance to the driving coil is changed and arranged in response to the number of windings of the coil. An apparatus for measuring magnetic strain rate of a steel sheet in an annealing furnace.

[10] The annealing steel sheet is annealed by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. A magnetic strain rate measuring device for measuring the magnetic strain rate of a steel sheet before heat treatment at

A drive coil for constructing a closed circuit having a large area having a size equal to or more than a plate width using an air core and transmitting an AC drive signal to the surface of the steel sheet;

A receiving coil constituting a closed circuit having a large area having a size equal to or greater than a plate width using an air core, and receiving and measuring the driving signal reflected from the steel sheet;

Using the measured value of the drive signal measured by the receiving coil, a component having a phase of 0 ° and / or a phase of 90 ° with respect to the transmitted drive signal is extracted, and the magnetic field of the steel sheet is based on the phase component. An apparatus for measuring the magnetic transformation rate of a steel sheet in an annealing furnace having a measurement processing device for measuring the transformation rate.

[11] The magnetic transformation rate of the steel sheet is measured in front of the induction heating apparatus of the annealing furnace using the method for measuring the magnetic transformation rate of the steel sheet in the annealing furnace according to any one of [1] to [5].

A continuous annealing process for feeding forward control of the induction heating apparatus based on the measured magnetic transformation rate by the measurement processing apparatus.

[12] The magnetic transformation rate of the steel sheet is measured in front of the induction heating apparatus of the annealing furnace using the method for measuring the magnetic transformation rate of the steel sheet in the annealing furnace according to any one of [1] to [5].

A continuous hot dip galvanizing process for feeding forward control of the induction heating apparatus based on the measured magnetic transformation rate by the measurement processing apparatus.

According to the present invention, since an air core coil which does not use an iron core is used as the size of the plate width or more, it is lightweight and excellent in durability, and the average transformation rate can be measured in the plate width direction of the steel sheet. In addition, since the distance between the measuring device and the steel sheet is corrected using the signal of the receiving coil, and the magnetic transformation rate is obtained based on the distance after correction, the measurement accuracy of the magnetic transformation rate is also improved. By applying the present invention to a continuous annealing process or a hot dip galvanizing process, it is possible to stably feed-in control the induction heating even when there is a change in the magnetic transformation rate.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view explaining schematic structure of the magnetic transformation rate measuring apparatus of the steel plate in the annealing furnace of this invention.
It is a figure explaining the principle of the magnetic transformation rate measuring method in the magnetic transformation rate measuring apparatus shown in FIG.
3 is a perspective view illustrating an embodiment of the present invention.
4 is a partially enlarged view for explaining another embodiment of the present invention.
5 is a view for explaining the principle of the magnetic transformation rate measuring method according to another embodiment of the present invention.
FIG. 6 is a graph for explaining the relationship between the distance between the steel plate and the drive coil (mm) and the signal ratio (V '÷ V) according to another embodiment of the present invention.

(Form to carry out invention)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described. In addition, this invention is not limited to the following embodiment.

First, with reference to FIG. 1 and FIG. 2, the principle of the magnetic strain rate measuring apparatus and the magnetic strain rate measuring method of the steel plate in the annealing furnace used for this invention is demonstrated. FIG. 1: is a figure explaining the schematic structure of the magnetic transformation measuring apparatus 15 of the steel plate in the annealing furnace 2 of this invention. FIG. 2: is a figure explaining the principle of the magnetic transformation rate measuring method of the magnetic transformation measuring apparatus 15 of the steel plate shown in FIG.

As shown in FIG. 1, the magnetic transformation measuring apparatus 15 installed in the annealing furnace 2 measures the coil 5, the transmitter 9 (not shown), the voltmeter 10 (not shown), and the measurement. It has a processing apparatus 14.

The coil 5 is comprised from one drive coil (excitation coil) and two or more receiving coils. A drive coil is a coil which transmits the electromagnetic wave (drive signal) of alternating current to the surface of a steel plate. A receiving coil is a coil which receives and measures the drive signal reflected from the steel plate.

The coil 5 is formed in the hollow core 4 which does not use an iron core, through the conducting wire. Receiving coils make two receiving coils a pair and reverse the winding direction of each conducting wire. As the hollow core 4, a ceramic pipe, an alumina pipe, etc. are used, for example. The hollow core 4 is formed to penetrate through the furnace body of the annealing furnace 2 and is disposed at predetermined intervals in the plate direction. Here, a pair of coils are formed by passing a conductive wire between two ceramic pipes so that the surface parallel to the steel sheet 1 is formed, and the pair of coils are spaced a predetermined distance in parallel to the surface of the steel sheet 1. Posted in 3 trillion. The coil 5 disposed in the center is a drive coil (see reference numeral 6 in FIG. 3 described later), and the pair of coils 5 disposed on both sides thereof is a receiving coil (symbol 7, 8 in FIG. 3 described later). See). For example, the distance of two receiving coils and a drive coil shall be equal intervals.

In addition, the number of turns of each receiving coil may be different, and when setting it as a different number of windings, the distance of two receiving coils and a drive coil can be arrange | positioned differently, respectively. Thereby, even if the installation location in the annealing furnace 2 is narrow, a measuring apparatus can be provided without being influenced.

In the present invention, the receiving coil may form a plurality of sets by using a pair of receiving coils as a pair of receiving coils. By arranging a plurality of sets of receiving coils, the measurement accuracy is further improved. For example, when using two sets of receiving coils, as shown in FIG. 4, two sets of receiving coils 7, 8, 12, and 13 are arranged for the driving coil 6, and two sets of receiving coils are used. The distance between the coil and the drive coil is arranged to be different from each other.

The transmitter 9 is a power source connected to a coil (drive coil) and generating a sine wave of a predetermined frequency and current value. For example, sine wave transmitters and function generators.

The voltmeter 10 is connected to the coil (receiving coil) and measures the drive signal received by the receiving coil. For example, a lock-in amplifier.

The measurement processing apparatus 14 is an arithmetic unit which corrects the distance of a steel plate and a drive coil using the measured value of the drive signal measured by the receiving coil, and measures the magnetic transformation rate of a steel plate based on the corrected distance. Or the measurement processing apparatus 14 extracts the component which has a phase of 0 degrees and 90 degrees with respect to the transmitted drive signal from the measured value of the drive signal measured by the receiving coil, and based on a phase component It is a computing device that measures. That is, in the measurement processing apparatus 14, distance is correct | amended by the difference of the installation position of a some receiving coil, and the difference of the ratio (signal ratio) and phase angle of the signal of each coil. In addition, since the magnetic transformation rate measuring method in the measurement processing apparatus 14 is demonstrated in FIG. 2 mentioned later, it abbreviate | omits here.

In addition, the magnetic transformation measuring device 15 may further have a thermometer 11. When a thermometer is provided, since the measured value of steel plate temperature can be used for the magnetic transformation rate measuring method, it is possible to raise a measurement precision further. The thermometer 11 measures the surface temperature of the steel plate 1, for example, is a radiation thermometer.

The magnetic transformation measuring apparatus 15 arrange | positions three sets of coils 5 (one drive coil and two receiving coils), respectively, in parallel with the surface of the steel plate 1, and the transmitter which is not shown in figure in a drive coil, Voltmeters not shown are connected to the receiving coils, respectively. The magnetic transformation measuring apparatus 15 controls the transmission of the electromagnetic wave (signal) of the drive coil based on the input information by the magnetic transformation measuring process control apparatus (not shown). When the steel sheet passes in front of the magnetic transformation measuring device 15, a signal (drive signal) is issued to the steel sheet 1 by the drive coil, and the signal reflected by the steel sheet 1 is measured by the receiving coil. The distance between the steel sheet and the drive coil is corrected using the measured value of the drive signal measured by the measurement coil by the measurement processing device 14, and the magnetic transformation rate of the steel sheet is obtained based on the corrected distance. On the other hand, when the steel sheet does not pass in front of the magnetic transformation measuring device 15, the signal emitted by the drive coil is canceled by the receiving coils connected in reverse phase, so that the signal is sent to the measurement processing device 14. Does not come out.

Alternatively, in the case where the steel sheet passes in front of the magnetic transformation measuring device 15, 0 ° and 90 ° with respect to the drive signal transmitted by the measurement processing device 14 from the measured value of the drive signal measured by the receiving coil. The component having the phase of is extracted and the magnetic transformation rate is obtained based on the phase component. On the other hand, when a steel plate does not pass in front of the magnetic transformation measuring apparatus 15, the signal sent to the measurement processing apparatus 14 does not come out similarly to the above.

In addition, when it applies to a continuous annealing process or a continuous hot dip galvanizing process, before the steel plate passes through the induction heating apparatus of an annealing furnace, the magnetic transformation rate of the steel plate is measured, and the measured magnetic field is measured by the measurement processing apparatus 14. Feed forward control is performed to transmit the rate of transformation to the subsequent induction heating apparatus.

In addition, although the transmission of the drive coil in the above-described magnetic transformation measuring device 15 is based on a constant value, when the received signal (that is, the measured value of the measured drive signal) at the receiving coil is too large or too small In this case, the magnitude of the transmission of the drive coil can be controlled by the magnetic transformation measurement process control device. For example, the signal of the drive coil is switched to one tenth or ten times by the overrange or underrange of the receive signal of the receive coil.

According to the present invention, the driving coil and the receiving coil for measuring the magnetic transformation rate of the steel sheet are made of an air core coil which does not use an iron core, and a loop which reciprocates a path such as crossing the annealing furnace. This is excellent. In addition, since the drive coil and the receiving coil investigate signals according to the magnetic transformation rate over the entire width of the steel sheet, the average transformation rate (that is, the average plate width direction magnetic transformation rate of the steel sheet) can be measured in the sheet width direction of the steel sheet. There is also an effect.

In addition, since the receiving coils are measured by connecting two receiving coils in pairs and connecting them in reverse phase, a signal of noise passing through the receiving coil is canceled out. Thereby, the magnetic signal of a steel plate can be measured clearly.

Next, with reference to FIG. 2, the principle of the magnetic transformation rate measuring method of the steel plate in this invention is demonstrated.

The magnetic transformation rate of a steel plate is measured using the phenomenon which changes from paramagnetic to ferromagnetic with steel transforming from an austenite phase to a ferrite phase.

In the present invention, first, the drive coil is controlled by the magnetic transformation measurement processing control device of the magnetic transformation rate measuring device 15 through the controller. And the drive coil 6 sends an electromagnetic wave (drive signal) toward the steel plate 1.

The reflected waves w ₁ and w ₂ from the steel sheet 1, which are affected by both the plate thickness directions and reflect from the surface side of the steel sheet ₁ , are incident on the two receiving coils 7, 8. In the receiving coils 7 and 8, signals are generated by the incident reflected waves w ₁ and w ₂ , and thus the magnitude of each signal is measured by the voltmeter 10.

Next, the distance between the steel plate 1 and the respective receiving coils 7 and 8 from the difference in the magnitude of the reflected waves w ₁ and w ₂ received by the receiving coils 7 and 8 by the measurement processing device 14. To calculate. Here, as shown in FIG. 2, the receiving coils 7 and 8 are connected in reverse phase by making the distance from the steel plate 1 different. For this reason, the signal generated in the receiving coils 7 and 8 cancels out. In addition, since noise signals passing through the receiving coils 7 and 8 are also canceled, noise can be prevented. However, since the radio wave attenuates with distance, the signal generated by the drive coil 6 is not completely canceled by the receiving coil 7 and the receiving coil 8, and only the signal from the steel sheet can be obtained.

Therefore, in this invention, the sum signal of the receiving coils 7 and 8 is measured, and the displacement amount from the reference position of the steel plate 1 is calculated using only the signal V which entered the steel plate. And based on the calculated displacement amount, the distance of the steel plate 1 and the magnetic transformation measuring apparatus 15 is computed. In addition, "the reference position of a steel plate" points out the position of the steel plate 1 shown by the dotted line in FIG. 2, and points out the position of the steel plate in the case of the state pulled loose without a sheet roll. In addition, in FIG. 2, it displaces by the arrow shown by the both sides shown.

Next, by using the calculated distance, the measurement processing device 14 corrects the signal V incident on each of the receiving coils 7 and 8 to a signal corresponding to the case where the steel sheet is at the reference position. The correction signal V ₁ is calculated. For example, the calibration curve of the signal ratio recorded in advance in the storage unit of the magnetic transformation rate measuring device 15 and the correction signal V ₁ are compared, and the steel sheet is obtained from the relationship diagram between the steel sheet temperature and the phase change caused by the transformation rate. Calculate the magnetic transformation rate of. As the calibration curve, one or more signals may be appropriately selected, and the distance between the steel sheet and the coil may be obtained from the signal ratio. For example, as compared to 100% of the case of using the signal of a ferrite plate and a 100% austenite steel sheet on the night on, the calculated correction signal (V ₁₎ obtained in the standard plate position (the reference position of the steel sheet), steel plate The magnetic transformation rate of the steel sheet is calculated from the relationship diagram between the phase change by temperature and the transformation rate.

In addition, the estimated value which the control system of a CAL and a CGL process calculates, for example as a steel plate temperature is used here. On the other hand, as described above, the thermometer 11 may be provided in the magnetic transformation rate measuring device 15. In this case, the temperature of the steel sheet is measured by a thermometer 11 provided before the steel sheet 1 passes through the three sets of coils 5 of the magnetic transformation measuring device 15 of the present invention. Then, using the measured steel sheet temperature and the phase change (correction signal V ₁ ) calculated by the measurement processing apparatus 14, the steel sheet temperature and transformation are measured in advance and recorded in the storage unit of the magnetic transformation rate measuring apparatus 15. The transformation rate of a steel plate can be calculated from the relationship diagram of the phase change by rate.

Further, in the present invention, a component (V90 °) having a phase of 90 ° with respect to the transmitted drive signal (excitation signal) is extracted from the signal V (total signal) incident from the steel sheet as described above, and the transformation rate is determined. Calculate. This is because the 90 ° phase component signal is based on Faraday's law of electromagnetic induction and reflects the magnitude of the magnetic properties of the steel sheet. The relationship between the steel sheet temperature and the phase change due to the transformation rate is compared with the calibration curve recorded in advance in the storage unit of the magnetic transformation rate measuring device 15 using the extracted component (V90 °) having the phase of 90 degrees. The magnetic transformation rate of the steel sheet can be calculated from the figure. In addition, the phase component may be different from the case where the incident signal is different due to the different magnetic state because the signal V incident from the steel sheet may be different even if the measurement position is different even with the same steel sheet. . Therefore, attention is paid only to the difference in magnetic properties by extracting the phase component. In the present invention, the use of the phase component of 90 ° is because the influence of the magnetic properties of the steel sheet is most included on the signal received by the receiving coil.

In the present invention, the signal (V) incident from the steel sheet is a component (V0 °) having a phase of 0 ° with respect to the transmitted drive signal (excitation signal) and 90 ° with respect to the transmitted drive signal. It extracts by dividing into the component (V90 degree) which has a phase. Then, the ratio (V90 ° / V0 °) is obtained from the extracted component (V0 °) having the phase of 0 ° and the component (V90 °) having the phase of 90 ° to receive the drive signal (excitation signal). The phase angle of the signal received by the coil is calculated. The magnetic transformation rate of the steel sheet is calculated using the calculated phase angle. In addition, the phase component of 0 ° is used because it mainly includes the influence of the resistance of the steel sheet. The use of the phase component of 90 ° is because, as described above, the magnetic signal of the steel sheet is most included in the total signal V received by the receiving coils 7, 8. In addition, using a phase angle (arctan (V90 ° / V0 °)) obtained from V90 ° / V0 ° uses a steel sheet and a measurement position in calculating the magnetic transformation rate using a phase angle different from the steel sheet state to be measured. This is because the magnitude of the signal due to the distance of? Is not affected by the magnitude of the signal of the drive coil.

Although the case where a pair of receiving coils is used here was demonstrated here, as mentioned above, you may use 2 or more sets of receiving coils of a pair. In this case, the above-described correction accuracy is improved than in the case of a set of receiving coils, and thus a more accurate magnetic transformation rate can be measured. In addition, since the specific measuring method at the time of using two sets of receiving coils is demonstrated in Example 2 mentioned later, it abbreviate | omits here.

According to the present invention, since the driving coil and the receiving coil are disposed on the same side with respect to the steel sheet, the driving signal reflected from the steel sheet receives the driving signal reflected by the steel sheet. The size varies depending on the position of the receiving coil disposed away from the steel sheet. Therefore, by arranging two receiving coils so that the path lengths of electromagnetic waves differ, the distance of a steel plate and a receiving coil is calculated | required from the difference of the magnitude | size of the drive signal received by the two receiving coils. Thereafter, by correcting the signal of the receiving coil at the distance, the magnetic transformation rate can be obtained from the signal of the correcting receiving coil. At this time, by using two sets of two pairs of receiving coils in reverse phase as the receiving coils, the correction accuracy is improved, and a clearer signal can be obtained. As a result, the measurement accuracy of the magnetic transformation rate is also improved.

In addition, the signal of the receiving coil combines the influence of the magnetic property of the steel plate with the influence of the induced current flowing through the steel plate. When the signal of the drive coil is a sine wave, the magnitude and phase of the signal differ depending on the temperature and the transformation rate of the steel sheet. Therefore, according to this invention, the phase component of 90 degrees is extracted with respect to the drive signal (excitation signal) which most contained the influence of the magnetism of a steel plate from the sum signal of the drive signal which the receiving coil received. Accurate magnetic transformation rate can be obtained by calculating the magnetic transformation rate from the size of the extracted 90 ° phase component or the size of the steel sheet reference position correction.

According to the present invention, the drive signal received by the receiving coil is measured by dividing the drive signal (excitation signal) into a signal having a 0 ° phase component and a signal having a 90 ° phase component and calculating the ratio. Accordingly, the phase angle of the received drive signal with respect to the drive signal (excitation signal) is calculated, and the influence of the position of the steel plate and the drive coil, specifically, the signal due to the distance between the coil group (drive coil, receiving coil) and the steel plate Regardless of the magnitude of, the rate of magnetic transformation can be obtained.

As mentioned above, according to this invention, since the drive coil and the receiving coil were made into the air core which does not use an iron core, what is necessary is just to arrange | position the lightweight coil comprised only of conducting wires across a continuous annealing furnace. As a result, even in an atmosphere heated to about 900 ° C., the measurement can be stably performed without being damaged by the weight of the coil.

Moreover, from the response and the ease of signal processing, the signal emitted from the drive coil is, for example, a sine wave, a square wave, a pulse or the like at a constant frequency. According to this invention, when a drive coil and a receiving coil are arrange | positioned and measured in either side with respect to the front and back surface of a steel plate, it sets two receiving coils. These two receiving coils are arranged at positions symmetrical with respect to the drive coils, and they are connected in opposite phases. Accordingly, the signals generated in the two receiving coils by the drive coils can be canceled (cancelled) in the two receiving coils. In addition, since the noise signal passing through the two receiving coils can also be canceled (cancelled), the noise can be prevented. At this time, the signal emitted from the drive coil is reflected on the steel plate, and the reflected signal is incident on two receiving coils to emit a signal. Since the distance from the steel sheet is different in the two receiving coils, and the magnitude of the generated signal is also different in the two receiving coils, when the total signal of the two receiving coils connected in antiphase is measured, only the signal incident from the steel sheet It is available.

In addition, according to the present invention, two sets of receiving coils connected in an antiphase can be arranged so that they can be arranged at different distances from the driving coils. In this case, since the distance between the drive coil and the receiving coil of each pair is different, the displacement from the reference position of the steel sheet can be calculated using the difference in the ratio of the reflected signal (signal incident to the receiving coil) from the steel sheet. . By using the calculated displacement, by correcting the influence from the position of the steel plate to the magnitude of the signal of the receiving coil, a more accurate magnetic transformation rate can be measured as compared with the set of receiving coils.

The signal emitted from the drive coil and reflected from the steel sheet is generated by the eddy current generated in the steel sheet, but the reflected signal differs in magnitude and phase from the original signal by the magnetic and electrical resistance of the steel sheet. In the case of ferromagnetic steel, the magnetic influence of the steel sheet is largely shown in the 90 ° phase component with respect to the drive signal of the receiving coil. Therefore, in the present invention, since the transformation rate of the steel sheet is determined by using the magnitude of the component having a phase of 90 ° with respect to the drive signal, the magnitude of the magnetism of the steel sheet can be measured clearly. In addition, accurate magnetic transformation rate can be measured.

Moreover, according to this invention, the measured signal is divided into each component of 0 degree phase and 90 degree phase with respect to a drive signal, and a transformation rate is calculated | required by the ratio or the phase of the measured signal with respect to a drive signal. Thereby, accurate magnetic transformation rate can be measured without being influenced by the change of the magnitude | size of the signal resulting from the position change of a steel plate.

The magnetic strain rate measuring apparatus and the magnetic strain rate measuring method of the present invention described above can be applied to a continuous annealing process or a continuous hot dip galvanizing process. In this case, the magnetic strain rate can be grasped by measuring the magnetic strain rate in the annealing furnace of the continuous annealing process or in the furnace of the continuous hot dip galvanizing process and before the solenoid type induction heating apparatus for reheating. Thereby, the influence on the induction heating apparatus can be calculated beforehand from the measurement result of the magnetic transformation rate of the steel sheet, and it can be controlled to suppress the voltage fluctuation of the induction heating apparatus.

In addition, temperature conditions, such as heating, a crack, cooling, and a plating process, in a continuous annealing process and a continuous hot dip galvanizing process of this invention are not specifically limited, A well-known condition can be employ | adopted.

According to this invention, the magnetic transformation rate of a steel plate can be known in an annealing furnace. Accordingly, in the continuous annealing process or the hot dip galvanizing process, the influence on the induction heating apparatus due to the magnetic transformation rate can be known in advance before the solenoid induction heating is performed. In addition, by performing feed forward control of the induction heating apparatus, induction heating can be stably performed even if there is a change in the magnetic transformation rate.

Hereinafter, with reference to FIGS. 3-6, the detail of this invention is demonstrated using each Example. In addition, this invention is not limited to a following example. 3 is a view for explaining an embodiment of the present invention, Figures 4 to 6 are views for explaining another embodiment of the present invention.

Example 1

As shown in FIG. 1 mentioned above, the steel plate 1 is annealed, changing the inside of the furnace body of the vertical type continuous annealing furnace 2 to the hearth roll 3. In this example, the steel sheet is heated to 800 ° C. and cooled to 600 ° C. by a gas jet, and then the coil 5 (drive coil 6, receiving coils 7, 8) of the magnetic transformation measuring device 15 of the present invention. Passed)).

In this example, the width of the furnace 2 is 2.5 m, and the steel sheet 1 uses a sheet width of 1 to 1.8 m. In addition, six ceramic pipes 4 penetrating the furnace body of the continuous annealing furnace 2 are formed, and the conductive wires are passed between the two ceramic pipes 4 so that the conductive wires are wound around the plane parallel to the steel plate 1. Thus, three sets of coils 5 are formed. In order to form one coil loop, two tanks of the ceramic pipe 4 were arrange | positioned at 0.5 m away in the board | substrate direction. The ceramic pipe 4 had an outer diameter of 30 mm, an inner diameter of 24 mm, and a length of 2000 mm, and passed a copper alloy wire having a conductor diameter (diameter) of 2 mm for 10 turns therein. This ceramic pipe 4 has a weight of about 5 kg in one piece. However, copper alloy wires are very small in diameter and have low rigidity, and there is a fear of wheels. In this invention, in order to suppress the curvature amount of a copper alloy wire, tension was provided in the flange part provided in the furnace wall with respect to the copper alloy wire. Thus, since the copper alloy wire did not touch the inner wall of a ceramic pipe, it was able to install stably.

3, the detail of the magnetic transformation measuring apparatus 15 in the vertical type continuous annealing furnace 2 in one Example (henceforth Example 1) of this invention is shown. As shown in FIG. 3, the three sets of coils 6, 7 and 8 were disposed in parallel to the surface of the steel sheet 1. The coil 6 is a drive coil, and the coils 7 and 8 are receiving coils. The distance of the steel plate and the drive coil was 200 mm from the steel plate. The drive coil 6 is connected to the power supply (sending machine) 9 which produces a sine wave of frequency 55 Hz and current 1A, and functions as a drive coil. The receiving coil 7 was arrange | positioned near the steel plate 1 only 100 mm rather than the drive coil 6. On the other hand, the receiving coil 8 was arrange | positioned in the position far from the steel plate 1 rather than the drive coil 6 only the same distance, ie, 100 mm, between the drive coil 6 and the receiving coil 7.

The receiving coil 7 and the receiving coil 8 are electrically connected so that the winding direction of the conducting wire is reversed, and the signals (reflected waves) reflected from the drive coil 6 by the voltmeter 10 (w ₁ , w ₂ ) It was set as one set of receiving coils measuring the size of the. In this way, since the signal generated in the receiving coils 7 and 8 is canceled by receiving the radio wave (drive signal) emitted from the driving coil 6 by connecting the winding direction in the opposite direction, the signal is It does not come out. In addition, among the signals generated by the noise in the background, signals caused by noise passing through the receiving coils 7 and 8 are also weakened by connecting the winding direction in the opposite direction.

On the other hand, when there is a steel plate, the electric wave emitted from the drive coil 6 is reflected by the steel plate 1 via a distance of 200 mm. The receiving coil 7 is further passed a distance of 100 mm from the steel plate, and the receiving coil 8 is reached through an additional 300 mm distance from the steel plate. At this time, since the radio wave attenuates according to the distance, the signal generated by the drive coil 6 is not completely canceled by the receiving coil 7 and the receiving coil 8. For this reason, only the signal from a steel plate can be obtained.

In order to make the influence of this attenuation stronger, the arrangement distance with respect to the steel plate conveyance direction of the two ceramic pipes 4 which comprise the drive coil 6 may be made shorter. However, in the present Example 1, the arrangement distance with respect to the steel plate conveyance direction in three sets of coils 6, 7, 8 was made the same from the viewpoint of a construction and maintenance property.

In addition, in this Embodiment 1, since each receiving coil 7 and 8 has the same winding number, it arrange | positioned equidistantly with respect to the drive coil 6. The number of turns of each of the receiving coils 7 and 8 may be different. The receiving coils 7 and 8 may be arranged at different distances so that the signal from the drive coil 6 is canceled in accordance with the number of turns. By doing in this way, even if the installation place of three sets of coils of the magnetic transformation measuring apparatus 15 is restrict | limited by the surrounding influence to install, the receiving coils 7 and 8 can be provided according to installation conditions.

As described above, the drive coil and the receiver coil of the present invention irradiate a signal corresponding to the magnetic transformation rate over the entire width of the steel sheet. Therefore, the average transformation rate (plate width direction average magnetic transformation rate of a steel plate) can be measured in the plate width direction of a steel plate.

In the first embodiment, the conducting wire of the coil is once repeatedly taken out of the furnace body and then traversed the furnace repeatedly. In order to reduce the influence of the steel shell, which is a magnetic substance, the inner side of the steel shell may be wound around. In addition, in this embodiment, since the bar is almost uniform, the influence is canceled by the reverse connection of the receiving coils 7 and 8, and this is not a problem. Here, iron bar refers to the surface of the iron plate which forms an annealing furnace.

In the first embodiment, the voltmeter 10 uses a lock-in amplifier. In the voltmeter 10, the measurement was performed by dividing the voltage signal V0 with a phase of 0 ° and the voltage signal V90 with a phase of 90 ° based on the phase of the drive current signal.

In the present Example 1, the surface temperature of a steel plate is measured by the thermometer 11 provided before the steel plate 1 passes three coils 5 of the magnetic transformation measuring apparatus 15 of this invention.

The transformation rate of the steel sheet from the relationship between the steel sheet temperature measured as described above and the phase change calculated by using the phase change calculated by the measurement processing apparatus and recorded in the recording section of the measurement processing apparatus and the like, and the phase change by the transformation rate. It can be seen. Specifically, V0 and V90 of the measurement voltage (V = V0 cosωt + V90 sinωt) are separately measured using a lock-in amplifier. From this measured value, arctan (V90 ° / V0 °) is obtained and evaluated. In addition, in Example 1, the phase angle was ± 2 °, and the difference in transformation rate ± 1% could be measured.

In addition, since the steel plate 1 during a measurement vibrates slightly between the hearth rolls 3, the distance between the steel plate 1 and the coil 5 of the three sets of the magnetic transformation measuring apparatus 15 also changes. For this reason, the signal measured by the voltmeter 10 also fluctuates. In the present Example 1, it could measure stably by performing the time average process of 3 second.

On the other hand, as a comparative example, the transformation amount measuring apparatus in the form shown in Example 4 (seventh figure) of patent document 2 (Unexamined-Japanese-Patent No. 59-188508) which drives at 55 microseconds is a vertical type | mold. Installed in a continuous heat treatment furnace. In this case, the sensor functional part (corresponding to three sets of coils referred to in the present embodiment) of the transformation amount measuring device is an external dimension of 80 × 80 × 200 mm and a weight of 10 kg. In order to protect this sensor function part from the heat of an annealing furnace, the water-cooling protection box (outside dimension: 200 * 200 * 500 mm, total weight: 50 kg) which encloses this sensor function part is needed. It was necessary to install this water-cooled protection box so that the distance of a steel plate and a protection box may be 100 mm at the tip of the support | pillar extended from the side wall of an annealing furnace. Therefore, long term installation construction including reinforcement of furnace wall was necessary for this setting.

In the case of the comparative example, since the structure supported the heavy object as a support, the sensor function part vibrated under the influence of the vibration of the roller or the like for conveying the steel sheet, and generated a large vibration with an amplitude of about 20 mm estimated at resonance during low-speed conveyance. I was. This effect caused cracks in the base of the prop and dropped out in 2 months.

In the case of the present invention shown in Example 1 described above, the three sets of coils 5 in the magnetic transformation measuring device 15 are lightweight ceramic pipes and conductive wires, and no vibration occurred when transferring the steel sheet. As a result, even the use of organs was not as bad.

Example 2

4 is a side view showing another embodiment (hereinafter, referred to as Embodiment 2) of the present invention.

As shown in FIG. 4, in this Example 2, one set of receiving coils 12 and 13 are added. In addition, since the other structure is the same as that of Example 1, description is abbreviate | omitted.

The receiving coils 12 and 13 are connected in the same manner as described above with the winding direction reversed. In the receiving coils 12 and 13, the magnitude | size (voltage V ') of the signal from the drive coil 6 is measured by the voltmeter not shown. In FIG. 4, the distance between the steel plate 1 shown by the solid line and each of the receiving coils 7, 8, 12, 13 or the driving coil 6 is 100 mm in the receiving coil 12 and the receiving coil 7, respectively. Is 200 mm, 300 mm for the drive coil 6, 400 mm for the receive coil 8, and 500 mm for the receive coil 13.

The radio wave (drive signal) emitted from the drive coil 6 is reflected by the steel plate 1 and enters each of the receiving coils 7, 8, 12, 13 as reflected waves w ₁ , w ₂ , w ₃ , w ₄ . do. As shown in FIG. 5, the distances from the steel sheet 1 to the respective receiving coils 7, 8, 12, 13 are different. In addition, the receiving coils 7-8 and 12-13 of each pair are connected in reverse winding directions, respectively. Therefore, the ratios V '÷ V of the signals V and V' obtained in each pair of receiving coils differ depending on the position of the steel sheet 1. In addition, "depending on the position of the steel plate 1" means the distance (mm) between a steel plate and a drive coil.

In the present Example 2, the signal which generate | occur | produced in each set of receiving coils 7-8 and 12-13 was measured by dividing into 90-phase voltage signals V90 and V90 'based on the phase of a drive current signal. And the signal ratio (V90 '/ V90) was measured about the steel plate which is 100% ferrite phase, and the steel plate which 50% is austenite phase, respectively.

Here, about the measurement result about the steel plate which is 100% ferrite phase, for example, the vertical axis | shaft was shown in FIG. 6 with signal ratio (V90 '/ V90), and the horizontal axis | shaft as distance (mm) between a steel plate and a drive coil. 6 shows that the distance between the steel plate and the driving coil can be specified from the signal ratio. In this invention, the magnitude | size of the signal of each receiving coil 12 and 13 is correct | amended using the distance between this steel plate and a drive coil. The magnetic transformation rate of the steel sheet can be obtained by comparing the corrected signal with the magnitudes of the signals of the steel sheet of 100% ferrite phase and the steel sheet of 100% austenite phase, which are obtained at the reference position of the steel sheet in advance. Here, although it demonstrated using the case where the ferrite phase is 100%, the case where ferrite phase: 70% + bainite phase: 30% etc. is selected suitably, for example.

In addition, similarly to the above, also in the second embodiment, the number of turns of the receiving coils connected to the pair may be different. Thereby, since each receiver coil can arrange | position a distance with respect to a drive coil differently, the occupation volume of the magnetic transformation measuring apparatus 15 containing a receiver coil can be made small. Moreover, the restriction | limiting of an installation place can be alleviated.

And also in 50% (gamma) steel, the same characteristic was acquired within +/- 1% compared with FIG. In other words, the distance could be measured without depending on the γ ratio.

Example 3

In the present Example, the magnetic transformation measurement apparatus 15 shown in Example 1, 2 mentioned above was applied to the continuous hot dip galvanizing process. The magnetic transformation measuring device 15 was installed in the final stage of the cooling zone before the molten zinc pod. In the magnetic transformation measuring apparatus 15, the time variation rate of the measured magnetic transformation rate was computed, and the change of the magnetic transformation rate, ie, the change of the magnetic characteristic by the austenite fraction variation, was calculated | required. And when the change of the magnetic characteristic by austenite fraction variation exceeds a preset threshold, the output of control was changed so that a voltage change might be suppressed before the steel plate part passes a solenoid type induction heating apparatus. . As a result, when the steel sheet portion passes, the response speed of the control was slowed so that the output variation did not excessively respond, and the induction heating control could be stably performed. As a result, it was possible to heat in the target heating temperature fluctuation range.

Thus, as a comparative example, the intervention in the control by the above-described magnetic transformation rate signal of the present invention was stopped. As a result, the induction heating of the austenitic fraction fluctuation portion exceeding the threshold was conducted under normal control, and the control system excessively responded and became unstable, deviating from the target heating temperature fluctuation range.

1: steel sheet
2: continuous annealing furnace
3: hearth roll
4: ceramic pipe
5: coil
6: drive coil
7: receiving coil
8: receiving coil
9: transmitter
10 voltmeter
11: radiation thermometer
12: receiving coil
13: receiving coil
14 measuring device
15: magnetic transformation device

Claims (12)

The steel sheet is heat-treated in the annealing furnace by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. As a method of measuring the magnetic transformation rate of the steel sheet before
By the drive coil which has the magnitude | size more than the plate width which used the air core, the drive signal of an alternating current is sent to the surface of a steel plate,
The drive signal reflected from the steel sheet is measured by a receiving coil having a size equal to or greater than the width of the plate using an air core,
An annealing for correcting the distance between the steel plate and the drive coil using a measurement value of the drive signal measured by the receiving coil by a measurement processing device and measuring the magnetic transformation rate of the steel plate based on the corrected distance Method for measuring the magnetic transformation rate of the steel sheet in the furnace. The method of claim 1,
The receiving coil is a magnetic transformation rate measurement method of a steel sheet in an annealing furnace in which two receiving coils are paired and connected in a reverse phase to a position symmetrical with respect to a driving coil to measure the reflected drive signal. The method according to claim 1 or 2,
As the receiving coils, two sets of two receiving coils connected in reverse phase are used, and the distances of the two sets of receiving coils and the driving coils are differently arranged,
By the said measurement processing apparatus, based on the measured value of the said drive signal in the said two sets of receiving coils, each distance of the said steel plate and said receiving coil is computed, and the said magnetic transformation rate is based on the calculated result. A method of measuring the magnetic transformation rate of a steel sheet in an annealing furnace to be corrected. The steel sheet is heat-treated in the annealing furnace by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. As a method of measuring the magnetic transformation rate of the steel sheet before
By the drive coil which has the magnitude | size larger than the plate width using a hollow core, an AC drive signal is sent to the surface of a steel plate,
The drive signal reflected from the steel sheet is measured by a receiving coil having a size equal to or greater than the width of the plate using an air core,
By the measurement processing device, the measured value of the drive signal measured at the receiving coil is divided into components having a phase of 90 ° with respect to the transmitted drive signal, and is based on the component having the phase of 90 °. A magnetic strain rate measuring method of a steel sheet in an annealing furnace, characterized by measuring the magnetic strain rate of the steel sheet. The method of claim 4, wherein
The said measured value is divided into the component which has a phase of 0 degree, and the component which has a phase of 90 degree with respect to the said drive signal sent by the said measurement processing apparatus, respectively, A magnetic transformation rate measuring method of the steel plate in an annealing furnace which measures the said magnetic transformation rate based on the ratio of the component which has a phase of 90 degrees. The steel sheet is heat-treated in the annealing furnace by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. As a magnetic strain rate measuring device for measuring the magnetic strain rate of the steel sheet before
A drive coil for constructing a closed circuit having a large area having a size equal to or more than a plate width using an air core and transmitting an AC drive signal to the surface of the steel sheet;
A receiving coil constituting a closed circuit having a large area having a size equal to or greater than a plate width using an air core, and receiving and measuring the driving signal reflected from the steel sheet;
An annealing furnace having a measurement processing apparatus for correcting a distance between the steel plate and the driving coil by using the measured value of the drive signal measured by the receiving coil and measuring a magnetic transformation rate of the steel sheet based on the corrected distance Magnetic transformation rate measuring apparatus of the steel plate in the middle. The method of claim 6,
The apparatus for measuring magnetic strain of a steel sheet in an annealing furnace wherein the receiving coils are connected in reverse phase to two receiving coils in pairs and symmetrical with respect to the driving coils. The method according to claim 6 or 7,
An apparatus for measuring the magnetic transformation rate of a steel sheet in an annealing furnace, wherein two sets of two receiving coils connected in reverse phase are used as the receiving coils, and the distances of the two sets of receiving coils and the driving coils are different from each other. The method according to any one of claims 6 to 8,
And said receiving coil changes the winding number of the coil for each receiving coil and changes and distances from said drive coil in correspondence with the winding number of said coil to arrange the magnetic transformation rate of the steel sheet in said annealing furnace. The steel sheet is heat-treated in the annealing furnace by using a drive coil disposed on one side of the surface of the steel sheet and a receiving coil disposed parallel to the surface of the steel sheet on the same side of the drive coil and on both sides of the drive coil. As a magnetic strain rate measuring device for measuring the magnetic strain rate of the steel sheet before
A drive coil for constructing a closed circuit having a large area having a size equal to or more than a plate width using an air core and transmitting an AC drive signal to the surface of the steel sheet;
A receiving coil constituting a closed circuit having a large area having a size equal to or greater than a plate width using an air core, and receiving and measuring the driving signal reflected from the steel sheet;
Using the measured value of the drive signal measured by the receiving coil, a component having a phase of 0 ° and / or a phase of 90 ° with respect to the transmitted drive signal is extracted, and the magnetic field of the steel sheet is based on the phase component. An apparatus for measuring the magnetic transformation rate of a steel sheet in an annealing furnace having a measurement processing device for measuring the transformation rate. The magnetic transformation rate of a steel plate is measured in front of the induction heating apparatus of an annealing furnace using the measuring method of the magnetic transformation rate of the steel plate in the annealing furnace in any one of Claims 1-5.
A continuous annealing process for feeding forward control of the induction heating apparatus based on the measured magnetic transformation rate by the measurement processing apparatus. The magnetic transformation rate of a steel plate is measured in front of the induction heating apparatus of an annealing furnace using the measuring method of the magnetic transformation rate of the steel plate in the annealing furnace in any one of Claims 1-5.
A continuous hot dip galvanizing process for feeding forward control of the induction heating apparatus based on the measured magnetic transformation rate by the measurement processing apparatus.

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